stunning news about lance armstrong. The u.S. Anti-doping agency is STRIPPING AWAY HIS SEVEN TOUR de France titles and banning armstrong from cycling for life, after the cyclist said he will no longer contest charges that he used drugs to boost his performance. Neal karlinsky has been on the story since the start. Reporter: The u.S. Anti-doping agency says it's official. Lance armstrong, one of the most famous athletes in the world, used drugs to fuel his win. Then, led a wide-ranging conspiracy to keep his team on top. The reality is, there's so much cheating going on in sports, just because you don't fail a drug test, doesn't mean you're not cheating. It's a really important day for clean athletes. It sets an important reminder that if you cheat with dangerous, performance-enhancing drugs, you're going to be held accountable. And your decision to dope does pay. Reporter: Armstrong spent a small fortune on the case, fighting and losing in court. He was left with no good options. Either face an open hearing and possibly damning testimony, or refuse to participate. Today in a statement he writes, enough is enough. Today, I turn the page. I will no longer address this issue, regardless of the circumstances. He believes the process is one-sided and unfair. Armstrong says the agency has no power to take away his yellow jersey. I know who won those seven tours, he writes. If he used the drugs that the anti-doping agency claims, how did he do it? Floyd landis told us, he performed blood transfusions during the tour. Claims armstrong has denied. This is a sad day in sport. When you think of lance armstrong, you think of what he means to so many people, especially those fighting cancer. Reporter: This may be just the tip of the iceberg. Sources tell us, armstrong may face two civil suits, seeking millions of dollars in damages, accusing armstrong of being a fraud. The story not over yet. Neal, thanks very much.

This transcript has been automatically generated and may not be 100% accurate.

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